This invention relates to fiber-optics and more specifically to underwater connection of fiber-optic cable to a light source.
Fiber-optic illumination is used in a variety of underwater applications. First, fiber-optic illumination may be used to bring light to a region which is too remote or otherwise inaccessible to an underwater lamp or other lighting system. Fiber-optic illumination allows light to be brought to an underwater location without invading the area with hazardous electrical cables or bulky battery packs. Fiber-optic illumination is of great benefit to underwater applications which require the transmission of light along a non-linear path. Moreover, fiber-optic illumination allows light to be transmitted over far greater distances underwater than a beam of light transmitted directly through the water which would otherwise be subject to dissipation by the volume and cloudiness of the water traversed. The use of fiber-optic transmission also eliminates the possibility of interference of the transmitted light by objects moving within the water.
Beyond visual illumination, fiber-optic light transmission greatly enhances the use of light for control and signalling applications. Underwater photoelectric controls are one specific application which is improved through the use of fiber-optic illumination. Underwater systems which transmit data, such as telephone or computer communication, similarly benefit from the use of fiber-optic light transmission.
Fiber-optic light transmission requires a light source at one end of the fiber-optic cable. In many underwater applications, it is advantageous to have the light source located underwater to minimize the distance over which the fiber-optic cable must carry the light to reach the desired location. The underwater location of the light source necessitates housing it within an enclosure capable of maintaining a watertight seal. Such an enclosure keeps water from contacting the electrical connections associated with the light source. The enclosure may also house a power supply to power the light source. A single enclosure may house a plurality of light sources powered either by a single power source or individually.
Fiber-optic cables, however, lack tensile strength due to their small diameter and are thus prone to breakage from either rough movement or repeated bending. Underwater applications present a harsh environment for fiber-optic cables as the cables tend to be flexed repetitively by even relatively calm water motion. Where fiber-optic cables are used by workers as underwater flashlights, the repeated maneuvering in such use leads to a short cable life. The short fiber-optic cable life necessitates frequent replacement of fiber-optic cables.
Typical connection, however, between the fiber-optic cable and the light source within the underwater enclosure, requires a cumbersome and time consuming procedure to replace a fiber-optic cable. To bring the fiber-optic cable to a position in which the light from the light source can be transmitted through the cable fiber-optically, it has been the practice to run the fiber-optic cable into the watertight enclosure through an opening which pierces the wall of the watertight enclosure. However, in order to protect the light source, its power supply, and any electrical components from contact by the surrounding water, the opening through which the fiber-optic cable passes must be sealed watertight after the fiber-optic cable is in place. Typically, a gasket must be installed to surround the fiber-optic cable where it passes through the opening to achieve this watertight seal. Alternatively, a gel must be applied to the junction of the opening and the fiber-optic cable passing through it. To bolster a watertight seal both approaches may be used in combination to minimize leakage. Unfortunately, neither method, nor their cumulative effect when used in conjunction, can absolutely ensure against leakage. Gels are prone to break down or wash away over time, and gaskets are prone to shrink or become brittle and fracture. Gaskets are further prone to develop tiny fissures or cracks, not readily detected upon inspection, which may allow seepage to occur. The high pressure associated with deep water locations, and the erosion associated with the turbulent water locations both increase the speed and likelihood of such seal failures.
Replacement of the fiber-optic cable in such systems necessarily breaks the watertight seal of the enclosure when the fiber-optic cable is removed from the enclosure opening. This leaves the electronic components exposed to water through the opening. Additional procedures are thus necessitated to safeguard the electrical components within the enclosure prior to removal of the fiber-optic cable being replaced. In applications in which the fiber-optic system is in a vessel or a tank, partial draining of such vessel or tank may be required to prevent water from entering the enclosure when the fiber-optic cable is removed. Alternatively, electrical components within the light source enclosure may be protected only by completely removing the entire enclosure from the water prior to removal of the fiber-optic cable.
In either case, after replacement of the fiber-optic cable has been accomplished, a watertight seal must again be established between the newly installed fiber-optic cable and the opening in the enclosure through which it passes. In systems using a gasket, the gasket must be reinstalled or perhaps replaced. In gel systems, the gel must be reapplied prior to re-submerging the light source enclosure to its underwater location. In addition to being time consuming, these additional sealing procedures necessitate the availability of the requisite sealing supplies whenever a fiber-optic cable must be replaced.
It can be appreciated from the foregoing that a need exists for an underwater coupling between a light source and a fiber-optic cable which eliminates the chance of leakage at the fiber-optic cable connection point, which allows the fiber-optic cable to be replaced without necessitating the removal of the light source enclosure from its underwater location, and which protects the enclosed electrical components from contact with the surrounding water during underwater fiber-optic cable replacement.